Sound-magnifying appliance for telephonic and telegraphonic purposes.



Y H. SMITH. v SOUNDIVIGNWYING APFLIANCE FOR TELEPHQNIC AND IELEGFH'ZMCAwucnion riz/au mags. wir;A

l, l 13,499. IDL-wanted Gail. 2.213. l'..

HARALD SMITH, 0F MAGDEBURG, GERMANY.

SOUND-MAGNIFYING APPLIANCE `FOR TELEPHONIE AND TELEGRAPHONIC PURPOSES.

Specification. of Letters Patent.

Patented Oct. 13, 1914.

Application filed April 18, 1914. Serial No. 832,676.

To all whom t may concern.'

Be it known that I, HARALD SMITH, a citizen of the German Empire,residing at Magdeburg, in Germany, have invented certain new and usefulImprovements in Sound- Magnifying Ap liances for Telephonie andTelegraphonic urposes, o-f which the following is a specification. p

The object of this invention is to provide improved means for increasingthe sound emitted by telephone receivers or produced by so-calledtalking magnets, the invention being applicable both to ordinarytelephone systems andjn systems with electromagnetic talking apparatus(telegraphones).

I use a diaphragm adapted to be vibrated by electromagnetic means, withmicrophones at each side of the diaphragm, comprising caj'tbonballsplaced within insulators which do not touch the diaphragm, so thatthe latter can vibrate freely across its entire diameter from wall towall of the box containing same. I electrically connect the microphonesat opposite sides of the diaphragm to two groupsof induction coils, sothat the current from the microphones on one side flows through theself-inductive coils in the opposite direction to the current flowingthrough thev other coils from the microphones on the other side. In thiscon-` nection I have found that it is not necessary to provide theinduction coils with secondary windings, but that better results areobtained by dispensing with secondary coils and connecting the telephonebetween the coils through which the current flows in opposite directionsas described.

The invention is illustrated in the accompanying drawings, in which- 1Figure 1 is a diagram of one installation in vertical section embodyingmy invention; Fig. 2 is a diagram showing another installation. Fig. 31s a sectional view of a detail, and Fig. 4 is a detail plan viewshowing three pairs of microphones on one side ot' the diaphragm andarranged in parallel.

Referring in the first instance to Fig. 1, 1 designates a Vdiaphragm ofcarbon, arranged ina box 2`of lead or other metal, which is forpractical purposes free from vibration. At opposite sides of themembrane are placcd'microphones 3, each consisting of a `cup ofelectrically insulating material, such as vulcanitc, with its cavityfaci g the diaphragm and containing a bloc 4 of carbon and two layers ofsmall carbon balls 5 on the'said block. The microphone cups are spacedfrom the diaphragm, so that the latter can vibrate. An iron rod or core6 fixed to the diaphragm de ends from the latter into a solenoid coilits downward movement being limited by an adjustable screw 8. The rod 6and screw 8 are polarized by means of an electromagnet 9 of cylindricalshape, ha'ving pole-pieces 10, 11, with holes for passage of :the rod 6and screws 8 respectively. Above the diaphragm, outside the box there isanother solenoid 12, with a core13 extending into the box and alinedwith the rod 6. The solenoid 13 is connected by a wire 121 to the screw8, and by a wire 1211 to one terminal of a battery 14, and the diahragxn is connected by a wire 15 to the otlier terminal of the battery.It' the parts 6 and S come into contact, and tend to make the diaphragmstick they close the circuit dcgcribed, and the core 13 pulls thediaphragm ree.

The microphones 3 are connected to cach other in pairs. Two groups ofinduction coils 16 and'l'? are provided, and the three pairs ofmicrophones (see Fig. 4) on one side of the diaphragm are connected bywires 18 to tlie coils 16, the three pairs on the other side beingconnected to the coils 17 by wires 19. As-shown in Fig. 1, the wires 18are joined to the right hand ends of the coils 16, and the wires 19 arejoined to the left hand ends of the coils 17. The opposite ends of thetwo groups of coils are connected by wires 2O and 21 respectively to oneterminal of the battery 14. Condensers 22 and '23 are connected to thecoils 16 and 17 re spectively, at the ends where connection made to thewires 18 and 19, and these cor.- densers are connected by wires 24 andQ5 re- Lmectively to a telephone 26. i t

vWhen the apparatus is in use, downward u'lovemcnt of the diaphragmincreases the resistance of the microphones 3 above it, andf thusreduces'the current in the coils 16, but increases the currentl in thecoils 17. Upward moyement of the diaphragm eiiects the currents in theopposite sense. The variations of current strength, due to movements ofthe diaphragm, produce induced currents in the coils. I have found thatthe secondary circuits need not be taken through separate coils, butthat the coils 16, 17 may be used therefor, a secondary circuit being,for example, formed as follows z-Coil 16, wires 20, 21', coil 17condenser 23, wire 25, telephone 26, wire 24, condenser 22, and back tothe coil 16.

F ig. 2 slows two of the sound magnifying applia ces arranged in series.One of these appl'ances is similar to that shown in Fig. 1,'an hasL adiaphragm 11, solenoid 71,

battery 141, and induction coils 161, 171, together with the respectivemicrophones, connections and condensers. The other appliance consists ofa. similar combination of elements, including a diaphragm 1", solenoid7, battery 14 and induction coilsl 16 and 17. vThe solenoid 7 is in thesecondary circuit of the first-mentioned appliance, and consequentlyinduces vibrations of the diaphragm l, which affect the currents in thecoils 16a and 17. These currents excite a talking magnet 30, which actson a magnetic steel wire 31.

Fig. 3 shows a preferred form of construction of the microphones. Ametal cup 34 is screwed by means of a shank 35 to the box containing thediaphragm, part of this box ibeing shown at 2', and the shank is madefast by means of a nut 36, enabling the cup to be easily detached. Thecup contains the carbon block 4, on which are placed the carbon balls,and the latter lie in and between rings 33, so that the balls aresupported in columns, consisting of vertical series of balls resting oneupon the other. This prevents the balls from becoming jammed.

The operation of the arrangement shown in Fig. 1 will be largelyunderstood from the foregoing description, together with the followingrexplanation. Assuming the diaphragm 1 of electrical conducting materialto be moved upwardly, causing the carbon balls 5 of the microphones 3 onthe upper side of diaphragm 1 to be brought more closely together,thereby reducing the resistance and increasing the current in onedirection through the respective circuits including the three wires 18,coils 16, back through battery 14 to the diaphragm 1. At the same timethe currents through the respective circuits of the three pairs ofmicrophones 3 on the lower side of the diaphragm 1 are reduced due tothe increased resistance, by virtue of the carbon balls 3 of themicrophones on the lower side of the diaphragm 1 being more separatedfrom one another, whereby such reduced currents pass through therespective coils 17 in the direction opposite to the direction of thecurrents passing through the coils 16, the circuit through coils 17including the condensers 23, battery 14, lower microphones 3 and Wires19.

It will be noted that the respective coils 16 kare connected in parallelwith the respective coils 17 through the battery 14 and diaphragm 1. Theconnection of the telephone receiver 26, or talking magnet 30, or likeelectro-responsive device, is such that the respective coils 16 andcondensers 22 are connected in series with the respective coils 17 andcondensers 23. -By reason of the inductivelyl related coils 16, 17,being wound in opposite directions, the magnetization is kept lowthereby effecting a high amplification of the voice currents. Similaractions and interactions between the microphones 3, coils 16, 17,condensers 22, 23, and the electro-responsive device 26, take place whenthe diaphragm 1 moves downwardly, in which. case thev current throughthe respective coils 17 is greater than the current through therespective coils 16.

What I claim as my invention and desire to secure byl Letters Patent ofthe United States is:--v f 1. In apparatus for the purpose set forth, adiaphragm, microphones at opposite sides of said diaphragm, a coilconnected at one end to a microphone on one side of said diaphragm, acoil inductively related to said coil and connected at one end to amicrophone on the other side of saiddiaphragm, a source of electricenergy, means connected with said source and connecting said-coils inparallel, an electro-responsive device, and means connected to saidelectroresponsive device and connecting said coils in series.

2. In apparatus for the purpose Set forth, a diaphragm, microphones atopposite sides of said diaphragm, a coil connected at one end to amicrophone on one side of said diaphragm, a coil inductively related tosaid coil and connected at one end to a microphone on the other side ofsaid diaphragm, a source of electric energy, means connected with saidsource and said diaphragm and connecting said coils in parallel, anelectro-responsive device, and means connected withsaidelectro-responsive device and connecting said coils in series.

3. In apparatus for the purpose set forth, a diaphragm, microphones atopposite sides of said diaphragm, a coil connected at one end to'amicrophone on one side of-said diaphragm, a coil inductively related tosaid coil and connected at its end opposite to said one end to amicrophone on the other side of said diaphragm, a source of electricenergy, means connectedwith said source and said diaphragm andconnecting said coils'inl parallel, an electro-responsive device, andmeans connected with said electrorcsponsive device and connecting said\\c0ils in series. i

4. In apparatus for the purpose set forth,

a diaphragm, two groups of microphones.

inductivcly related to said group of coils and connected oppositely tothe group .of micropl'loncs on the other side of said dia- `phra, ,'m, asource of electric energy, means -coiinccted with said source and said'dia- ,liragm and connecting said rst named 'group of coils and saidsecond named group a coil connected at one end to the microprone at oneSide of said diaphragm, a coil connected at one' endto the microphone atthe other. side of 'said diaphragm, means electrically connecting theother ends of said coils to each other, an electric soundproducii'igappliance, and means including condensers connecting saidsound-producing appliances to said coils.

6. In apparatus for the/purpose set forth the combination of adiaphragm, a solenoid on' one side of said diaphragm, an iron rodattached to said diaphragm extending into said solenoid, an ironabutment alined with said rod in said solenoid to limit the vibration ofthe diaphragm, an annular group of electro-magnets surrounding saidsolenoid,`

pole pieces on said eleetromagnets embracing said rod and said abutmentrespectively, microphones at opposite -sides of said diaphragm, a coilconnected at one end to the microphone at one side of said diaphragm,

'a coil inductively related to said coil connected at one end to themicrophone at the other side of said diaphragm, a source of electricenergy, and means connected with said source and said diaphragm andconnecting saidcoils in parallel.

7. `In apparatus for the purpose set forth thecombination of adiaphragm, a solenoid on one side. of said diaphragm, an iron rodattached to said diaphragm extending into said solenoid, an ironabutment alined with said rod in said solenoid to limit the vibration ofthe diaphragm, an annular group of electromagnets surrounding saidsolenoid, pole pieces on said electromagnets einbracing said rod andsaid abutment respectively, microphones at opposite sides of saiddiaphragm, a coil connected at one end to the microphone at one side ofsaid diaphragm, a coil connected at one end to the microphone at theother side of' said diaphragm, means electrically connecting the otherends of said coils tov each other, a second solenoid on the other sideof Said diaphragm, a core in said second solenoid aliped with vthe rodattached to the diaphragm, and means whereby con- .tact of the lastmentioned rod with the iron abutment establishes an electric circuit 8.In apparatusifor the purpose set forth the combination of two groups ofelements,

each comprising a diaphragm, microphones at opposite sides of said diahragm, a solenoid, anY iron rod attache connected at one end to amicrophone atene side of said diaphragm, a coil inductively related tosaid coil-connected at one end to a microphone at the other side of saiddiaphragm, ascurce of electric energy, means connected to said sourceand connecting the coils of the two groups in parallel, and means forconnecting the solenoid of one of said groups with the coils of theother group of elements.

9. In apparatusfor the purpose set forth,-

to said dia'- phragm extending into said solenoid, a colli a diaphragmof conducting material, two

groups of microphones respectively on opposite sides of said diaphragm,two groups of inductively interrelated coils, the coils of one groupbeing connected to the microphones on one side of said diaphragm and thecoils of the other group being oppositely connected to the microphoneson the other side of said diaphragm, a source of electric energy, meansconnected with said source and said diaphragm and connecting the coilsof said two groups in parallel, an electro-responsive device, and meansconnected with said *electro-responsive device connecting said coils inseries.

10. In apparatus for the purpose set forth, a diaphragm, groups ofmicrophones at op- /posite sides of said diaphragm, the microphones ofeach gro-up being arranged in parallel, groups of inductively relatedcoils, the coils of one group bein microphones on one side of saiddiaphragm, the' coils of the other group being oppositely connected tothe microphones ,on the other side of said diaphragm, condensers con.nected to said groups of co1ls,.a source of electric energy, and meansconnected with saidsouree and 4connecting said groups of coils inparallel.

connected to the 11. In apparatus for the purpose'set forth,

a diaphragm of conducting material, groups of microphones at oppositesides of said daphragm, the microphones 'of each group being arranged inparallel, groups of indue tively related coils, the coils of one groupbeing connected to the microphones on one side of said diaphragm, thecoils-of the other group being oppositely connected to the microphoneson the other side of diaphragm, condensers connected'tosaid groupf ofcoils, a sourceof electric energy, and

means connected with said source and said diaphragm and connecting saidgroups of coilsin parallel.

. 12 In apparatus for the purpose set forth, a diaphragm, two groups ofmicrophones disposed respectivelv on the opposite side of CTY group beinconnectedin'paallel, a coil connected to t e group Aof microphones ononecoils in series.' side of said diaphragm, a coil iductively re lated tosaid coil and oppositely connected to the group of microphones on theother side of said diaphragm, a. source offelectric energy, anelectrofresponsive device, and means connected with" seid'eleetxpoo-Iiesponsive device and connecting said groups of In witnesswhereof I have signed. this specification in the presence of two.witnesses.

` HARALD SMITH.

Witnesses: -v

HENRY EYOLEY, lL. OCHLMANN.

